The present invention relates to apparatuses having a current generating device by which a predetermined current can be forced to flow into a device which is connected to it, and, respectively, a voltage generating device, by which a predetermined voltage can be applied to a device which is connected to it.
Apparatuses such as these have been known in innumerable embodiments for many years and require no further explanation.
They are used, inter alia, but, as is known, in no way exclusively, in integrated circuits, where they supply current or voltage either to the entire integrated circuit or to specific parts of the integrated circuit.
Current generating devices or voltage generating devices which are provided in integrated circuits do not need to be active all the time. This may be for two reasons: either because the respective currents or voltages produced by the current generating devices or voltage generating devices are required only in response to specific events (for example for programming a flash memory), or because the devices which are supplied with power from the current generating devices or from the voltage generating devices need or should not always be in operation.
Circuits or circuit parts which need or should not always be in operation are frequently switched to an energy saving operating mode, such as a so-called sleep operating mode or a so-called power-down operating mode, at times in which they are not required. In these operating modes, the relevant circuits or circuit parts are switched to a state in which they consume less power, or no power whatsoever. This allows the power consumption, and heat that is produced, to be reduced.
There are various options for switching a circuit or a circuit part to an energy saving operating mode. The current generating device or voltage generating device which supplies power to the relevant circuit or the relevant circuit part is preferably deactivated for this purpose; this allows the power consumption and the amount of heat produced to be reduced to the maximum extent.
Circuits or circuit parts which are switched to an energy saving operating mode can be reset to the normal operating mode again when required, in which as the title itself makes evident, they are supplied with power in the normal way, and operate in the normal way.
Experience has shown that it takes a certain amount of time to switch a circuit or a circuit part from an energy saving operating mode to the normal operating mode. Therefore, it is necessary to wait for a greater or lesser time period after initiation of the operating mode switching process, before the relevant circuit or the relevant circuit part can be used as normal.
Since it is frequently not evident in advance whether, and possibly when, a circuit or a circuit part must be switched back to the normal operating mode, the switching process is generally initiated only at the time at which the relevant circuit or the relevant circuit part is required. However, since it is still necessary to wait for a certain time after this before the process of switching to the normal operating mode has been completed (until the relevant circuit or the relevant circuit part is once again operating, or can operate, correctly), switching to the normal operating mode is associated with a pause of greater or lesser duration, during which the integrated circuit which contains the relevant circuit or the relevant circuit part cannot operate, or in any case cannot operate at maximum power.
This is obviously a disadvantage.
It is accordingly an object of the invention to provide a current generating device and a voltage generating device which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, in which the switching of a circuit or of a circuit part from an energy saving operating mode to the normal operating mode can be sped up.
With the foregoing and other objects in view there is provided, in accordance with the invention, a current generating device. The current generating device has a circuit for generating a predetermined current that can be forced to flow into a device connected to the circuit. The predetermined current is different than a specific current which would otherwise flow, the predetermined current flowing temporarily into the device in response to a predetermined event.
The current generating device according to the invention is distinguished in that it is configured to force a current, which is different to that which would otherwise flow, to flow temporarily into the device which is connected to the current generating device, in response to the predetermined event, and the voltage generating device according to the invention is distinguished in that it is configured to temporarily apply a voltage, which is different to that which would otherwise occur, to the device which is connected to the voltage generating device, in response to a predetermined event.
Current generating devices and voltage generating devices such as these allow the circuit or the circuit part which is supplied with power in this way to be briefly supplied with a current or a voltage which speeds up the process of reaching the normal operating mode, after initiation of the switching process from an energy saving operating mode to the normal operating mode.
The fact that a circuit or a circuit part is supplied during the change in operating mode with a current or with a voltage which is higher or lower than the current or the voltage which the current generating device or the voltage generating device would force to flow or would apply if the fact that a change in operating mode is being carried out has not been signaled to it has been found to be advantageous from two points of view. First, in consequence, this makes it possible to overcome the defect associated with conventional current and voltage generating devices that, once these devices have been switched on, they do not immediately and directly supply the currents and voltages which they supply during steady-state normal operation and, second, the current generating devices and voltage generating devices can in consequence even supply currents and voltages during the change in operating mode which are intentionally higher or lower than the currents and voltages which are generated during steady-state normal operation of the current and voltage generating devices.
This makes it possible for the relevant circuit or the relevant circuit part to more quickly reach the state that it must assume in order to operate normally. In particular, this makes it possible for the capacitances in the circuit that is to be switched or in the circuit part that is to be switched, including any parasitic capacitances such as line capacitances (capacitances which are formed by the lines in the circuit or in the circuit part) and gate capacitances (capacitances at gate connections of field-effect transistors) to be charged, discharged or have their charges reversed more quickly than is required for correct operation of the circuit or of the circuit part. Furthermore, suitable currents and voltages at the source and/or drain connections of field-effect transistors make it possible to form a conductive channel more quickly in the relevant field-effect transistors.
The use of current generating devices or voltage generating devices configured as described, and suitable actuation of them, make it possible to switch a circuit or a circuit part from an energy saving operating mode to the normal operating mode in the shortest possible time. It is even possible to use the circuit to be switched or the circuit part to be switched as normal immediately (even in the next clock cycle).
In accordance with an added feature of the invention, the predetermined event indicates that the device connected to the circuit has switched from an energy saving operating mode to a normal operating mode. The device has at least one read amplifier for reading data stored in a memory device. The predetermined current which the circuit forces to flow into the device is temporarily greater or less than the specific current which the circuit would force to flow at a relevant time if the predetermined event had not occurred. The predetermined current which the circuit forces to flow into the device in response to the predetermined event is temporarily greater or less than the specific current which the circuit forces to flow into the device in a steady state.
In accordance with another feature of the invention, the circuit contains a current generator generating a given current. The circuit contains a transistor connected to the current generator such that the given current generated by the current generator flows through the transistor. The circuit additionally contains a further transistor through which the specific current that is not generated by the current generator flows. The transistor and the further transistor are configured and connected such that currents flowing the transistor and the further transistor are in a specific ratio to one another, and the specific current flowing through the further transistor is forced to flow into the device connected to the circuit. Preferably, the transistor and the further transistor are connected to form a current mirror.
In accordance with an additional feature of the invention, the circuit is constructed such that the transistor, through which the given current generated by the current generator flows, also has a further current which is not generated by the current generator and flows through the transistor when the predetermined event occurs. A switching device is provided, and the further current is produced by switching on the switching device. The switching device is connected in series with the transistor and through the transistor the given current generated by the current generator and the further current flow. An operation of the switching device results in an opening and closing of a given circuit containing the transistor and the switching device. The switching device is a transistor having a gate connection receiving a signal signaling an occurrence of the predetermined event, and in response to the signal, the predetermined current that is different to that which would otherwise flow is forced to flow into the device connected to the circuit.
In accordance with a further feature of the invention, a high-pass filter is connected to the switching device, and the signal controlling the switching device is applied to the switching device through the high-pass filter. Alternatively, a low-pass filter is connected to the switching device, and the signal controlling the switching device is applied to the switching device through the low-pass filter.
In accordance with a concomitant feature of the invention, the further transistor is one of a plurality of further transistors, the further transistors are connected to the transistor to form the current mirror.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a current generating device and a voltage generating device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.